Add 13 harvesters for the Pensoft suite of open journals

[erinspace]

Pensoft OAI PMH URLs from this list: http://arphahub.com/about/webservices

One file has 13 seperate harvesters. Some are older than others, and don't have a lot of new content. But it was easier to add them all in one swoop!

Also - made it so the harvester does not need an end date specified - these pensoft OAI endpoints broke when specifying an end date, so making them optional fixes this